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AF 447 Search to resume (part2)

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AF 447 Search to resume (part2)

Old 11th May 2011, 10:34
  #1141 (permalink)  
 
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Dave Senior,

I think you are overlooking the most obvious translation of the word Etrange which is "unknown".
I think you probably have a point here. That´s why I would like to see the original phrase.

Nevertheless, I have my doubts if an expert couldn´t have a good idea of the shark species by inspecting the bites. There are not many shark species making a life at high seas, and the most dangerous shark there is the oceanic whitetip, known to attack wrecked tripulations of ships and aeroplanes crashes.
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Old 11th May 2011, 10:38
  #1142 (permalink)  
 
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"...will be present at a May 12 press briefing. Held on the BEA's premises at Le Bourget, the briefing will discuss FDR findings"

Or should that read "The finding of", because any commitment to deliver any findings from the FDR on the same day it arrives back is either:
1- A massive management overcommitment that the investigators cannot sensible achieve; or
2- music to the ears of the conspiracy theorists - they have already pre-prepared the findings
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Old 11th May 2011, 10:49
  #1143 (permalink)  
 
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Originally Posted by Machinbird
If this can happen in an A320, why cannot the same thing occur in the A330?
I had a quick look at this report for refreshing my memory but this quote was a shortcut in the report. It looks like ADR3 was already rejected due to AoA wrong data (in fact good) by ADR1 & ADR2 vote (both being false due to blocked AoA probes). Then, at this point, they had only two ADRs left in opposite sides of the fuselage; hence when they started to vary due to abnormal attitude, none could be retained and the flight envelope protection was kicked off.
Consequently, this ADRs rejection was primary the result of the two probes already blocked, not this unusual attitude direct consequence (as you'll have two probes in the same side which should not be affected by disymetrical flight).
Originally Posted by Machinbird
As soon as the 3 ADRs are rejected, the RTL will be left at last value. This could likely occur in just a few seconds after the beginning of loss of control. Note: no freezing of pitot tubes is required to generate this situation!
Two ADRs rejected => ALT2. But yes, I can see what you mean now. Then, by what would have been caused this loss of control still in Normal Law? A rogue C-3PO being nasty?
I thought it was first due to (a false) overspeed (two blocked pitots) triggering an irrelevant flight envelope protection and a never ending pull up, reaching some 90°+ AoA, and killing all the speed in few seconds around FL600?

S~
Olivier
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Old 11th May 2011, 10:59
  #1144 (permalink)  
 
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Originally Posted by sensor_validation
It is strange to me that the violent manoeuvre by the A340 is assumed possible but very rare so the main recommendation was to not closely stack planes vertically just in case a lower one decides to climb without permission.
I'm not addressing the validity of the "violent manoeuvre" (those Gs' doesn't look very different for both aircraft) but the fact that this 340 was, a priori, in an real overspeed situation (going close to Mach 0.89) in those turbulences. Then a pitch up seems to me appropriate, manual or automatic (and better in auto mode if those pilots were shaken enough as not being able to monitor their speed, already too fast at the first place). Calling it an "overspeed" incident, might be more adequate but sound much less dramatic than an "AoA incident".
My concern is more about how does this event could be qualified as an "AoA incident", while the main problem I can see here was a TCAS conflict between two aircraft flying in a very tiny turbulent airspace?

S~
Olivier
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Old 11th May 2011, 11:00
  #1145 (permalink)  
 
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Originally Posted by oldengmkr
The A340 scenario, with a zoom climb resulting in decreased forward velocity followed by a deep stall, with perhaps even a tail down fall to the water, fits the roughly known envelope of AF 447. There does not seem to have been any aspects of this irrefutably rejected by the responses and counter comments provided to date in this thread - or did I miss something?
I have previously argued that the A340 airprox incident does not fit the AF447 scenario because triggering alpha-prot law disengages the autopilot and, in the case of AF447, that was immediately followed by reversion to ALT law. Since the High Angle of Attack protection is not available in ALT law, I assumed that the reversion would cancel alpha-prot if it had been activated prior to that point. Maybe we need to review that assumption?

EDIT:: If alpha-prot had been activated prior to reversion to ALT law, and continued to be active after that point, it would maintain AoA at alpha-prot, i.e. it would not lead to deep stall. On the other hand, it may have handed the pilots an aircraft at relatively high AoA, low speed and possibly unusual pitch attitude.

PS:: Think of QF32, where the protection 'recovered' the airplane to an AoA (minus 5 deg) that was well below the threshold it was intended to protect.

Regards,
HN39

Last edited by HazelNuts39; 11th May 2011 at 11:40.
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Old 11th May 2011, 11:41
  #1146 (permalink)  
 
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Originally Posted by HazelNuts39
Since the High Angle of Attack protection is not available in ALT law, I assumed that the reversion would cancel alpha-prot if it had been activated prior to that point. Maybe we need to review that assumption?
Me think that all flight envelope protections are active in Normal Law either A/P ON or OFF. It would take some pressure on the stick in order to overide them.

S~
Olivier
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Old 11th May 2011, 11:51
  #1147 (permalink)  
 
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Nevertheless, I have my doubts if an expert couldn´t have a good idea of the shark species by inspecting the bites. There are not many shark species making a life at high seas, and the most dangerous shark there is the oceanic whitetip, known to attack wrecked tripulations of ships and aeroplanes crashes.
Give me a break. While I am happy to participate in tactful discussions of a forensic nature where this may assist wider understanding, discussions about shark bites are devoid of significance and potentially distressing to "interested parties."
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Old 11th May 2011, 12:04
  #1148 (permalink)  
 
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Originally Posted by takata
this 340 was, a priori, in an real overspeed situation (going close to Mach 0.89) in those turbulences. Then a pitch up seems to me appropriate, manual or automatic (and better in auto mode if those pilots were shaken enough as not being able to monitor their speed, already too fast at the first place). Calling it an "overspeed" incident, might be more adequate but sound much less dramatic than an "AoA incident".
Maybe you need to read the Airprox report more thoroughly. The report says quite clearly that pitch-up was not due to the overspeed condition, but was caused by the "projected" AoA reaching alpha-prot, thereby activating the High Angle of Attack protection.

Regards,
HN39
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Old 11th May 2011, 12:11
  #1149 (permalink)  
 
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Originally Posted by Hazelnuts39
Maybe you need to read the Airprox report more thoroughly. The report says quite clearly that pitch-up was not due to the overspeed condition, but was caused by the "projected" AoA reaching alpha-prot, thereby activating the High Angle of Attack protection.
Oh! If you are right, maybe I should stop doing too many things at the same time! (and I can't even find the point I answered you in my previous post).
:-)
Olivier
[edit:
OK, I have read it more carefully and found what part confused me:
Suddenly the aircraft began to climb, the Master Warning sounded and the autopilot self-disengaged as the aircraft exceeded the speed limit of 0.86 Mach.
And then, looking at the FDR graphic, it is not that obvious (at this scale) that there was a small delay between this pitch up and the overspeed. Nonetheless, you was right about this AoA law which should not have been active in manual control. Speed, supposed to be Mach 0.82 (while turbulences were expected) seems nonetheless very high and very close to Mach 0.86 during all the sequence, don't you think? Anyway, I agree that something was very wrong about the triggering of those delayed actions/warnings. Neither do I see it "deep stalling" anywhere at FL372, 205 KIAS and 15° nose up, at whatever cg settings]

Last edited by takata; 11th May 2011 at 13:42.
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Old 11th May 2011, 13:11
  #1150 (permalink)  
 
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EDLB, you'd want to fire up the crystal oscillator nearly continuously to avoid the chirp and initial self heating effects. And it doesn't really help you that much if the RC oscillator is moderately stable with time over the 10 ms pulse. As long as you have the 10 ms pulse you are stuck with a 100 Hz or wider FFT window.

Actual window size needed varies with shape of the actual shaped FFT filter. Gaussian is best if you know the frequency. But you can't really get that with an FFT very well. So you have to compromise and accept enhanced filter ringing.

(That's an interesting subject to me since designing proof of concept military
Hedy Lamar radios. er that's frequency hoppers. She designed the concept with some help on details from George Antheil. To make a fast hopper work right you need VERY good filter ringing characteristics or other compromises. We'd chosen the Gaussian filter approach.)

With the crystal oscillator you can use count downs to transmit X cycles out of Y total cycles easily enough. Then, since it is counter controlled, you know what the signal looks like for optimal decoding. Alas, you don't know WHEN the signal looks like that. So you have to record and post process or use a boatload of GPUs. Then you have to sit very still (kill Doppler effects) for several seconds while a few pings could add up. Then you move and sit another 10 seconds. That sounds like a lot of effort for a few dB of non-coherent signal addition. At 50ppm a 37.5kHz crystal is roughly .05 Hz off. Um, you might get decent correlation gain. edit: Oops - misuse of calculator and didn't trust my intuition. It's closer to 1.9Hz so coherent addition may not happen depending on the period precise frequency at which you presume the crystal is operating. You might be better off trading transmission time for power and use processing gain to make up the difference and distinguish the signal from the general noise characteristics such as whale song.

I've a question for auv-ee if he's read this far. What are the noise power characteristics vs frequency for 100Hz through 100kHz. (I understand 100kHz is basically down to thermal noise levels.) And I'd LOVE to know some transducer sensitivity characteristics. Alas, I don't know where to look for this data.

{^_^}

Last edited by JD-EE; 11th May 2011 at 13:21.
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Old 11th May 2011, 13:15
  #1151 (permalink)  
 
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AAIB AIRPROX Report

HN39,

Re the AIRPROX report, I think some of us were not totally convinced by the AAIB's interpretation of the initial upset: their argument that turbulence caused a sudden increase in AoA sufficient to trigger phase-advanced Alpha-Prot.

We speculated that the pitch-up could have been due to overspeed protection. Then the AP tripped (for whatever reason). So the sequence would be roughly as follows:
(1) Overspeed protection causing pitch-up;
(2) AP disconnect (not sure why);
(3) lack of stick movement by PF allows a 1G trajectory, causing deceleration;
(4) Alpha-Prot is activated.

You remember my making reference to "phase-advance" in another context. We used to get phase-advanced stick-shake on the VC10 and BAC1-11. But I'm very surprised it could happen to the extent that the AAIB describes. (But I am. admittedly, often surprised!)

In haste,
Chris
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Old 11th May 2011, 13:17
  #1152 (permalink)  
 
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Slats11, for that matter why would somebody care about the damage to the corpse after it became a corpse enough to spend the money to call in said shark expert? It's silly. The description gives a general shape to the damage which is more than you and I or anybody else really needs to know.

{^_^}

(Unless said critter somehow got into the cockpit at 37000 feet and caused the incident.)

{O,o}
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Old 11th May 2011, 13:45
  #1153 (permalink)  
 
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grity

Reminds me of my Dad's story from his WWII USAAF days - the B-17 was occasionally used as a troop carrier. During one such flight at cruise everyone migrated to the rear to see the wonderful view from the gunner's bay - at which point the pilot ordered everyone to refrain from doing so immediately and to return to their assigned positions!
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Old 11th May 2011, 13:46
  #1154 (permalink)  
 
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Hi Chris,
Originally Posted by Chris Scott
Re the AIRPROX report, I think some of us were not totally convinced by the AAIB's interpretation of the initial upset: their argument that turbulence caused a sudden increase in AoA sufficient to trigger phase-advanced Alpha-Prot
Add me in, except that this event, quite serious though if they had collided, should not qualify as an "upset" per see!
:-)
Olivier
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Old 11th May 2011, 14:00
  #1155 (permalink)  
 
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Chris;

If I may venture into some speculation, my impression reading this report is that an AIRPROX report normally lands on the desk of an investigator with ATC background. He gets some help from Airbus to explain the response of the airplane, quote: "the corrected or phase-advanced angle of attack (a computed parameter which is not recorded but can be calculated by Airbus Industry from the DFDR data)". So I suggest what you are reading here has been faithfully noted 'straight from the horses mouth'.

I am slightly disappointed by Appendix B. The timescale is unreadable and, while the story is about Mach and AoA, there is no trace of either. There is a trace of a 'MMO Exced.' discrete, and I suspect the DFDR also contains discretes for alpha-prot and High Speed protection, which are not shown.

If you compare the 'Pitch' trace and 'MMO Exced.', the High Speed protection may have been triggered briefly, but the pitch trace really takes off after the Mmo exceedances at 14:21:50 hrs, ten seconds after AP disengage.

Regards,
HN39
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Old 11th May 2011, 14:02
  #1156 (permalink)  
 
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So you have to record and post process or use a boatload of GPUs
With todays computers I would be surprised if you couldn't easily process in real time. After all you can easily fft and square (power spectrum) 100 MHz bandwidth nyquist sample data in real time. Hence I would have thought for these trivial bandwidths it would be a walk in the park, some one would need to work out the flops.
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Old 11th May 2011, 14:18
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HN39,
did you noticed this sentence?
page10:
"Suddenly the aircraft began to climb, the Master Warning sounded and the autopilot self-disengaged as the aircraft exceeded the speed limit of 0.86 Mach."
This sound quite different later.
There is a drop in pitch (down) exactly at the same time as the overspeeding event. I'm not sure that Airbus was so involved in the wording of the report. They would have answered the specific questions from the investigators, no more.
What bother me is that an AoA protection would increase the AoA in this case. For what effect beside adding some drag and slowing down in the climb?

Last edited by takata; 11th May 2011 at 14:30.
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Old 11th May 2011, 14:35
  #1158 (permalink)  
 
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takata;

That sentence is from the captain's recollection of events, prior to analysis of the DFDR data. Did you notice this sentence on page 14? -
Aircraft response to turbulence -
Changes to the A340’s flightpath caused by the aircraft’s flight control system response to the overspeed warning and autopilot disconnect were negligible until AoA law was triggered.
Regards,
HN39

PS: Quote: "I'm not sure that Airbus was so involved in the wording of the report." I agree, the wording is AAIB's, but the substance is Airbus.

Last edited by HazelNuts39; 11th May 2011 at 14:53. Reason: PS
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Old 11th May 2011, 14:58
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Originally Posted by Hazelnuts39
That sentence is from the captain's report, prior to analysis of the DFDR data. Did you notice this sentence on page 14?
Indeed. (I re-read it)
It sounds like a confusion to me. AoA law should be triggered for AoA reduction during this climb as the speed is serioulsy decreasing. Hence, I doubt (without looking at the chart) that this 15° pitch up, 205 KIAS at FL372 would project something else than a stall (then why pitching up... in advance?).

Otherwise, at first, it should be an overspeed protection kicking after the excess speed was recorded. A/P kicking OFF should be due to excess G load in turbulence, then the weather may come in to contradict this AoA law if not avail. in manual. Hence, maybe a sudden G load could have delayed the sequence, confusing the pilot report (alpha prot /alpha floor), those investigators (AoA laws), then us (AF447 deepstallers, sharks and pingers storytellers) !!!

S~
Olivier
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Old 11th May 2011, 15:12
  #1160 (permalink)  
 
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From France24 site

France backpedals on Rio-Paris crash recovery efforts - AF447 CRASH - FRANCE 24


France backpedals on Rio-Paris crash recovery efforts

French teams working to recover the remains of the victims of the ill-fated Air France jet that crashed into the Atlantic in 2009 will only retrieve bodies that are not badly decomposed, according to a letter to families of the victims signed by the Paris judges overseeing the case.

The letter, a copy of which FRANCE 24 obtained on Friday, recognized that the decision to only recover certain remains was “contrary to certain public announcements relayed by the media” that all of the bodies would be brought to the surface and handed over to families.

On Friday, Brazilian defense minister Nelson Jobim told journalists in Rio de Janeiro that all of the remains that were found would be recovered. "We must then identify them and conduct DNA tests,” Jobim said.

French police later said that rescue teams would be reinforced, "to lift all the bodies and personal effects."

“Only if conditions allow”

Addressing family members of the victims, judges Sylvia Zimmermann and Yann Daurelle said: “You should know that the remains of the victims are understandably in a state of decomposition given the particularly violent crash, the time elapsed and the environment.

“Consequently, we will proceed only with the recovery of the bodies that can be returned to their families in a decent state, and only if conditions allow for their identification,” the judges letter continued.

Brazilian authorities have come under intense pressure from the group representing the Brazilian families of the AF 447 victims, which has demanded that all bodies be retrieved.

The French families did not make any immediate statements following the release of the judges letter.

.../...
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